1. Field of the Invention
The present invention relates to a spread illuminating apparatus, and more particularly to the spread illuminating apparatus used as an illuminating means for a liquid crystal display device.
2. Description of the Related Art
A demand for a liquid crystal display device operating in a low power consumption is increasing mainly for personal computers or portable telephones due to its low profile and light weight. Since a liquid crystal of the liquid crystal display device does not emit light by itself unlike a light emitting element such as a cathode-ray tube, a separate illuminating means is required besides the liquid crystal display device when observing images. In particular, a spread illuminating apparatus of side light type (light conductive plate type) is used as an illuminating means for the liquid crystal display device so as to satisfy the recent demand for the low profile as well as energy saving.
FIG. 4 shows an example of such a spread illuminating apparatus of side light type.
In FIG. 4, a spread illuminating apparatus 1, which includes a rectangular transparent substrate made of a light transmissible material, generally comprises a bar-like light source 4 disposed along one end face 3 of a transparent substrate 2 made of a light-transmissible material. The transparent substrate 2 formed into a plate-like rectangle has a light reflection pattern 5 on a surface (an upper side in FIG. 4).
The light source 4 is generally composed of a bar-like light conductive member 6 made of a transparent material and disposed close to and along the one end face 3 of the transparent substrate 2, and a spot-like light source 7 disposed on one end face of the light conductive member 6.
An optical path conversion means 8 is provided on the light conductive member 6. The optical path conversion means 8 comprises a plurality of grooves 9 which are, for example, triangular in section, and extended in the thickness direction (the vertical direction in FIG. 4) of the light conductive member 6, and formed in the longitudinal direction of the light conductive member 6 on a face 6b opposite to a transparent substrate opposing face 6a, and light emitted from the spot-like light source 7 is incident on the one end face 3 of the transparent substrate 2 in a substantially uniform manner. The depth of the grooves 9 triangular in section is in proportion to the increase in distance from the spot-like light source 7 being able to unify the light.
In order to improve the light utilization efficiency of the light conductive member 6, a frame 10 which is substantially U-shaped in section and has a light reflection member (not shown) inside thereof covers a surface of the light conductive member 6 except the transparent substrate opposing face 6a and also covers a proximal portion (a part on the end face 3 side) of the transparent substrate 2 thus collecting light beams leaked from the light conductive member 6.
In addition, the frame 10 also works not to detach the light conductive member 6 from the transparent substrate 2 with a specified strength. In order to reliably integrate the light conductive member 6 with the transparent substrate 2, the width L1 of the frame 10 is wider at least by 1 to 3 mm than the width L2 of the light conductive member 6 thereby covering the proximal portion of the transparent substrate 2. Accordingly, in the spread illuminating apparatus 1 in FIG. 4, the width L1 of the frame 10 is set to be 4 to 6 mm while the width L2 of the light conductive member 6 is 3 mm.
In the spread illuminating apparatus described above, the market thereof demands for obtaining a larger size of the liquid crystal screen as possible. Meeting the above demand, the frame covering portion over the liquid crystal screen should be as small as possible to the contrary. Thus, the reduction of the width L1 for the frame 10 will be one of the options to achieve the larger liquid crystal screen.
However, if the width L1 of the frame 10 is reduced as described above, the portion of the frame 10 overlapped with the transparent substrate 2 is reduced accordingly, whereby the required strength for integrating the light conductive member 6 with the transparent substrate 2 will be insufficient and not satisfy the recent demand.
The present invention has been made in light of the above problems, and the object thereof is to provide a spread illuminating apparatus in which a portion covering a liquid crystal screen is reduced to a minimum while surely integrating a light conductive member with the transparent substrate.
In order to solve the above problems, according to a first aspect of the present invention, there is provided a spread illuminating apparatus including a rectangular transparent substrate made of a light transmissible material, in which a bar-like light source comprising a bar-like light conductive member made of a transparent material and a spot-like light source disposed on one end face of the light conductive member is disposed along one end face of the rectangular transparent substrate and a frame is held on the transparent substrate so as to cover the light conductive member, wherein the light conductive member is wedge-shaped such that a width of one end thereof facing a spot-like light source is larger than a width of the other end opposite the one end; and the transparent substrate is structured such that one end thereof facing the light conductive member is inclined and has an inclination angle forming an obtuse angle with respect to one side thereof aligned to the one end of the light conductive member facing the spot-like light source.
According to a second aspect of the present invention, in the spread illuminating apparatus according to the first aspect of the present invention, the inclination angle of the transparent substrate is set to be substantially supplementary to the light conductive member inclination angle which is formed by one side of the light conductive member facing the transparent substrate with respect to the one end face facing the spot-like light source.
According to a third aspect of the present invention, in the spread illuminating apparatus according to the first or second aspect of the present invention, one light source is provided, and wherein the transparent substrate is trapezoid-shaped such that one side thereof aligned to the one end of the light conductive member facing the spot-like light source is shorter than the other side opposite to the one side.
According to a fourth aspect of the present invention, in the spread illuminating apparatus according to the first or second aspect of the present invention, two light sources are provided, and each of the two light sources is disposed along each of both ends of the transparent substrate opposite to each other.
According to a fifth aspect of the present invention, in the spread illuminating apparatus according to the fourth aspect of the present invention, respective one ends of respective light conductive members of the two light sources, which face respective spot-like light sources, are located to be aligned to one same side of the transparent substrate, and the transparent substrate is trapezoid-shaped.
According to a sixth aspect of the present invention, in the spread illuminating apparatus according to the fourth aspect of the present invention, respective one ends of respective light conductive members of the two light sources, which face respective spot-like light sources, are located to be aligned to respective sides of said transparent substrate opposite to each other, and the transparent substrate is parallelogram-shaped.